Internally cooled electrical machine with a cast winding head

Abstract

The invention relates to an electrical machine (1) having the features of patent claim 1 and to a method for producing a waveguide winding with a cast winding head (5).

Description

The invention relates to an internally cooled electric machine having a rotor and a stator with a hollow conductor winding and a hydraulic connection part for feeding in or collecting coolant, and to a method for producing such an electric machine. The invention further relates to an electrical device having a hollow conductor winding and a hydraulic connection part.BACKGROUND OF THE INVENTIONFrom the prior art, internally cooled electric machines with a hollow conductor winding are known, which is produced using pin or hairpin technology. The pins or hair pins are usually waveguides which are produced from copper and which are inserted into slots of the stator of the electric machine and which generate a magnetic field during operation of the electric machine. The waveguides have a continuous channel through which a coolant is conducted in order to cool the electric machine during operation.DE 10 2018 129 226 A1 shows, for example, an electric machine having a rotor and a stator having a waveguide winding. In addition, a hydraulic connection part with connections for a plurality of waveguides is described therein, by means of which a coolant can be fed into the waveguides and / or coolant emerging from the waveguides can be collected. The hydraulic connection part can be sealed by means of potting compound. However, the connection of the hollow conductors to the hydraulic connection part is implemented in a relatively complicated manner and can be simplified further.OBJECT OF THE INVENTIONIt is therefore an object of the present invention to provide an internally cooled electric machine having a hollow conductor winding, the hollow conductor winding ends of which can be electrically connected in a particularly simple manner and can be connected and sealed to a hydraulic cooling circuit.This object is achieved according to the invention by the features mentioned in claim 1. Further embodiments of the invention are evident from the dependent claims.According to the invention, an electric machine is proposed which comprises at least the following components:a rotor,a stator having a winding formed from hollow conductors through which a coolant is conducted in order to cool the winding during operation,at least one winding head on which open ends of the waveguides are arranged; anda hydraulic connection part to which the hollow conductors are hydraulically connected, wherein the hydraulic connection part has at least one channel via which a coolant can be fed into the hollow conductors or a coolant emerging from the hollow conductors can be collected. According to the invention, the winding head is cast in a casting compound, wherein the open ends of the waveguides protrude from the casting compound. According to the invention, the winding head does not comprise a pouring mould, such as a trough, into which the casting compound is introduced. The casting of the winding head is preferably produced with the aid of a tool which encloses the stator on its inner side and outer side and provides a space in the region of the winding head into which the casting can be introduced. The tool is removed again after the casting.All principles of this invention are applicable to any other electrical device having a waveguide winding for generating an electromagnetic field, such as transformers or inductors with a waveguide winding.The casting compound is preferably applied directly to the laminated core of the stator and preferably extends from the laminated core to just below the open ends of the waveguides. Optionally, an air gap can also be present between the casting compound and the laminated core, to which air gap the casting compound directly adjoins. Alternatively, a disk, such as a holding disk, for example, can also be present between the laminated core and the casting compound, which disk has passages for the individual waveguides.The hydraulic connection part is preferably at least partially embedded in the casting compound. By embedding the hydraulic connection part in the casting compound, it is simultaneously mechanically fixed and fluidly sealed.The hydraulic connection part can optionally be embodied in one part or in multiple parts. In a multi-part embodiment, feet or fastening bases can be provided, for example, which are embedded in the casting compound in a first step. A second part of the hydraulic connection part is then mounted on the feet or the fastening bases.In a preferred embodiment, the hydraulic connection part has web-like walls, which are partially immersed in the casting compound and enclosed by it.The walls can have an anchoring section which fixes the hydraulic connection part in the casting compound in a form-fitting manner. According to an embodiment, the anchoring portion can comprise one or more projections or transverse bores which project laterally away from the wall.The potting compound can comprise an epoxy resin, a thermoplastic or a silicone or a combination of a plurality of the materials mentioned. It is preferably electrically insulating.In addition to the hydraulic connection part, electrical connection elements which electrically connect the waveguides can also be embedded in the casting compound.In a specific embodiment, the at least one channel provided in the hydraulic connection part comprises first sections with a larger cross section and second sections with a smaller cross section. In the second sections there are preferably no waveguide ends.According to a first embodiment of the electric machine, only one of the end windings is cast. In a second embodiment of the electric machine, both end windings are embedded in casting compound. At at least one of the end windings, a hydraulic connection part is provided which is likewise embedded in the casting compound.The waveguides of the winding can be designed as rigid waveguide elements which are arranged in slots of the stator. Rigid waveguide elements are, for example, pins or hair pins with a continuous channel through which a coolant is conducted. However, the invention is also suitable for other winding types, such as for example for a concentrated winding or an inserted winding.In a special embodiment of the invention, the grooves are likewise encapsulated, i.e. the waveguides arranged in the grooves are encapsulated by the encapsulation compound.The hydraulic connection part can be formed in the shape of a trough and have web-like walls.The hydraulic connection part is preferably configured annularly as a hydraulic connection ring. Alternatively, it could also consist of individual angle segments.The hydraulic connection part can be made of plastic, for example, but also of metal.The individual waveguides are preferably open at their front ends, so that the coolant can be fed in at one of the ends at the front and can be designed at the other end at the front. However, the invention also functions for waveguides which are closed at the end and have a lateral tap.In a special embodiment, the hydraulic connection part comprises at least one coolant connection (feed connection), via which the coolant can be fed into the connection part from the outside, and a coolant connection (return connection), via which the coolant can be discharged to the outside.The hydraulic connection part preferably comprises a plurality of phase connections (L1-L3) which are electrically connected to the waveguides.A hollow conductor according to the invention is preferably made of copper, aluminum or an alloy of one of the materials mentioned. An electrically insulating layer is preferably provided on its outer surface.The hydraulic connection part preferably comprises a plurality of circumferential channels for distributing or collecting coolant into or from the individual hollow conductors.The invention further relates to a method for producing an electrical device, in particular an electrical machine, having a hollow conductor winding. According to the invention, the method comprises at least the following steps:casting a casting compound onto a portion of the electrical device on which open ends of the waveguides are arranged, such as an open end winding, so that the open ends of the waveguides protrude from the casting compound; and;allowing the casting compound to cure.Before or after the casting, one or more further components, such as a hydraulic connection part or electrical connection elements, can be positioned in the region of the cast section and embedded in the casting compound.In the case of an electric machine having a stator and a rotor, the potting compound of the open winding head can be produced by supplying a potting compound on the other side of the stator, that is to say on the other winding head, and then conducting the potting compound through the slots of the stator to the open winding head. In the simplest case, the casting compound flows by gravity from one winding head to the other. Preferably, a negative pressure is generated on the side of the open end winding, which vacuum pulls the casting compound from the other side of the stator through the slots to the open end winding.For the casting of the section, a tool can be used, for example, which houses at least the section of the electrical device on which the open ends of the waveguides are arranged-in the case of an electrical machine: the stator in the region of the open winding head-and defines a space into which the casting compound is filled. The tool is removed again after the casting compound has cured.In the case of an electric machine having a stator and a rotor, the potting compound of the open winding head can be produced by supplying a potting compound on the other side of the stator, that is to say on the other winding head, and then conducting the potting compound through the slots of the stator to the open winding head. In the simplest case, the casting compound flows by gravity from one winding head to the other. Preferably, a negative pressure is generated on the side of the open end winding, which vacuum pulls the casting compound from the other side of the stator through the slots to the open end winding.BRIEF DESCRIPTION OF THE DRAWINGSThe invention is explained in more detail below by way of example with reference to the attached drawings. The following are shown: FIG. 1 shows a sectional view of an electric machine with a hollow conductor winding according to a first embodiment of the invention, in which one of the two end windings is cast with a casting compound; FIG. 2 shows a sectional view of an electric machine with a hollow conductor winding according to a second embodiment of the invention, in which both winding heads are cast; FIG. 3 is an enlarged sectional view of the open end winding of the electric machine of FIG. 1 ; FIG. 4 shows a sectional view of a hydraulic connection part of the electric machine from FIG. 1 ; FIG. 5 shows an enlarged sectional view of the open end winding of an electric machine according to a further embodiment.FIG. 1 shows a sectional view of a three-phase electric machine 1 having a stator 2, a rotor (which is not shown for reasons of clarity) and a winding 4 formed from rigid hollow conductors 14 for generating an electromagnetic field. The rigid waveguides 14 are designed as hair pins in this example and comprise a continuous channel 21, through which a coolant is conducted in order to cool the electric machine 1 during operation. The hair pins are usually made of copper. The outer surface of the hair pins is provided with an electrically insulating coating. The phase terminals are denoted by L 1, L 2, and the third phase terminal L 3 is not illustrated.The stator 2 comprises, in a known manner, a laminated core 12 having grooves 13 in which the waveguides 14 are arranged. The waveguides 14 have open ends 6, which in this exemplary embodiment are all arranged on the same side of the stator 2 and form an open winding head 5 a thereat. The winding head 5 located on the other side of the stator 2 does not comprise open waveguide ends and can thus be referred to as a "closed" winding head 5 b.The stator 2 also comprises a hydraulic connection part 7 arranged on the open winding head 5 ato which the hollow conductors 14 are hydraulically connected. The hydraulic connection part 7 is of annular design and comprises two channels 8, via which coolant can be fed into the hollow conductors 14 and a coolant emerging from the hollow conductors 14 can be collected. In the exemplary embodiment shown, one of the channels 8 is a feed channel 15 via which the coolant is fed into the hollow conductors 14. The other channel 8 is a return channel 16, in which the coolant emerging from the hollow conductors 14 is collected. During operation of the electric machine 1, the coolant is fed into the connection part 7 from the outside via a coolant connection 10 (feed connection), then reaches the feed channel 15 and flows from there through the individual waveguides 14.As can be seen, the open end winding 5 ais partially cast in an electrically insulating casting compound 20, wherein the open ends 6 of the waveguides 14 protrude from the casting compound 20. The hydraulic connection part 7 is likewise partially embedded in the potting compound 20. This has the advantage that the hydraulic connection part 7 is simultaneously mechanically fixed and fluidly sealed by the potting compound 20. Further measures for fastening the connecting part 7 or for sealing it are not necessary.In the first embodiment shown in FIG. 1, the closed winding head 5 bshown at the bottom in the figure is not cast. FIG. 2 shows a second embodiment in which the closed winding head 5 bis also cast. In addition, in this embodiment, the sections of the waveguides 14 running in the grooves 13 are surrounded by potting compound 20. Apart from this, the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. 2 are identical, and therefore reference is made to the description of FIG. 1 with respect to the further components.FIG. 3 shows an enlarged sectional view of the open end winding 5 aof the electric machine 1 of FIG. 1, which shows that the hydraulic connection part 7 is designed as a trough-shaped element with web-like walls 9, which delimit the individual channels 8. Outer walls are provided with the reference numeral 9. An inner wall between the feed channel 15 and the return channel 16 is denoted by the reference symbol 9 a.FIG. 4 shows an enlarged sectional view of the open end winding 5 aof the electric machine 1. the sectional surface extends transversely to the longitudinal axis of the electric machine 1 through the hydraulic connection part 7, so that the internal structure of the connection part 7 can be seen easily. The hydraulic connection part 7 has a flow channel 15 and a return channel 16. The first and second portions alternate circumferentially. In segments in which one channel 15, 16 has a large cross section, the other channel 15, 16 has a second section with a small cross section. In the region of the first sections, a plurality of waveguide ends 6 are arranged in each case. No waveguide ends 6 are arranged in the region of the second sections. The channels 8 run substantially over the entire circumference of the hydraulic connection part 7.FIG. 5 finally shows yet another embodiment of an electric machine 1, in which the walls 9 comprise an anchoring section 19 in order to better fix the hydraulic connection part 7 in the potting compound 20. In the embodiment shown, the wall 9 has feet at its free end. Other positive connections can be realized in the same way.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2018 129 226 A1

[0003]

Claims

Electric machine (1) comprising: - a stator (2) with a laminated core (12) and a winding (4) formed from hollow conductors (14), through which a coolant is conducted in order to cool the winding during operation, and - at least one winding head (5) on which open ends (6) of the hollow conductors (14) are arranged; characterized in that - the winding head (5) is encapsulated with an encapsulation compound (20), - the winding head (5) does not have an encapsulation form for the encapsulation compound (20), - and the open ends (6) of the hollow conductors (14) protrude from the encapsulation compound (20).Electric machine according to Claim 1, characterized in that - the casting compound (20) either directly adjoins the laminated core (12) or - an air gap or a disc is arranged between the casting compound (20) and the laminated core (12), to which air gap or disc the casting compound (20) directly adjoins.Electric machine according to Claim 1 or 2, characterized in that a hydraulic connection part (7) is provided, which is at least partially embedded in the potting compound (20).Electric machine according to Claim 3, characterized in that the hydraulic connection part (7) comprises undercuts in order to fix it in the casting compound better.Electric machine according to one of the preceding claims, characterized in that the casting compound (20) comprises an epoxy resin, thermoplastic or a silicone.Electric machine according to one of the preceding claims, characterized in that some of the waveguides (14) in the region of the open winding head (5a) are electrically connected to other ones of the waveguides (14) via electrical connection elements, wherein the connection elements are likewise embedded in the potting compound (20).Electric machine according to one of the preceding claims, characterized in that the stator (2) comprises two end windings (5), both of which are embedded in casting compound (20).Electric machine according to Claim 1, characterized in that the stator (2) is likewise encapsulated with potting compound (20) in the region of its grooves (13).Electric machine according to one of the preceding claims, characterized in that the hydraulic connection part (7) is formed in the shape of a trough, has openings, and has partitions for the coolant guidance and distribution.Electrical device having a winding (4) formed from waveguides (14) for generating an electromagnetic field, which winding has at least one section at which open ends (6) of the waveguides (14) are arranged, and having a hydraulic connection part (7) to which the waveguides (14) are hydraulically connected; characterized in that - at least the section is encapsulated with an encapsulation compound (20), wherein - the open ends (6) of the waveguides (14) protrude from the encapsulation compound (20).Method for producing a waveguide winding, which comprises a section at which open ends (6) of the waveguides (14) are arranged; characterized byat least the following steps: - casting at least the section with a casting compound (20), such that the open ends (6) of the waveguides (14) protrude from the casting compound (20); - allowing the casting compound (20) to cure.Method according to claim 11, wherein the step of pouring comprises supplying the casting compound (20) on the side of a first winding head (5) and passing through the slots (13) of a stator (2) and to an opposite winding head (5, 5a).

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